1,913 research outputs found

### Q-instantons

We construct the half-supersymmetric instanton solutions that are
electric-magnetically dual to the recently discussed half-supersymmetric
Q7-branes. We call these instantons `Q-instantons'. Whereas the D-instanton is
most conveniently described using the RR axion \chi and the dilaton \phi, the
Q-instanton is most conveniently described using a different set of fields
\chi' and T, where \chi' is an axionic scalar. The real part of the Q-instanton
on-shell action is a function of T and the imaginary part is linear in \chi'.
Discrete shifts of the axion \chi' correspond to PSL(2,Z) transformations that
are of finite order. These are e.g. pure S-duality transformations relating
weak and strongly coupled regimes. We argue that near each orbifold point of
the quantum axion-dilaton moduli space PSL(2,Z)\PSL(2,R)/SO(2) the higher order
R^4 terms in the string effective action contain contributions from an infinite
sum of single multiply-charged instantons with the Q-instantons corresponding
to the orbifold points \tau=i,\rho where \tau is the complex axion-dilaton
field.Comment: 29 pages, 1 figur

### p-Branes, D-Branes and M-Branes

We consider solutions to the string effective action corresponding to
p-Branes, D-Branes and M-Branes and discuss some of their properties.Comment: 8 pages, latex, uses sprocl.sty; talk given at the Workshop on Gauge
Theories, Applied Supersymmetry and Quantum Gravity (London, July 1996) and
the Strings '96 conference, ``Current Trends in String Theory'' (Santa
Barbara, July 1996

### Seven-branes and Supersymmetry

We re-investigate the construction of half-supersymmetric 7-brane solutions
of IIB supergravity. Our method is based on the requirement of having globally
well-defined Killing spinors and the inclusion of SL(2,Z)-invariant source
terms. In addition to the well-known solutions going back to Greene, Shapere,
Vafa and Yau we find new supersymmetric configurations, containing objects
whose monodromies are not related to the monodromy of a D7-brane by an SL(2,Z)
transformation.Comment: 31 pages, 3 figure

### Domain Walls on the Brane

We show that all branes admit worldvolume domain wall solutions. We find one
class of solutions for which the tension of the brane changes discontinuously
along the domain wall. These solutions are not supersymmetric. We argue that
there is another class of domain wall solutions which is supersymmetric. A
particular case concerns supersymmetric domain wall solutions on IIB D-5- and
NS-5-branes.Comment: 18 pages, Tex, uses phyzz

### Massive IIA supergravity from the topologically massive D-2-brane

The superfield equations of massive IIA supergravity, in the form of
constraints on the superspace geometry, are shown to be implied by
$\kappa$-symmetry of the topologically massive D-2-brane.Comment: 19 pp. Minor corrections. To appear in PL

### Non-extremal D-instantons

We construct the most general non-extremal deformation of the D-instanton
solution with maximal rotational symmetry. The general non-supersymmetric
solution carries electric charges of the SL(2,R) symmetry, which correspond to
each of the three conjugacy classes of SL(2,R). Our calculations naturally
generalise to arbitrary dimensions and arbitrary dilaton couplings.
We show that for specific values of the dilaton coupling parameter, the
non-extremal instanton solutions can be viewed as wormholes of non-extremal
Reissner-Nordstr\"om black holes in one higher dimension. We extend this result
by showing that for other values of the dilaton coupling parameter, the
non-extremal instanton solutions can be uplifted to non-extremal non-dilatonic
p-branes in p+1 dimensions higher.
Finally, we attempt to consider the solutions as instantons of (compactified)
type IIB superstring theory. In particular, we derive an elegant formula for
the instanton action. We conjecture that the non-extremal D-instantons can
contribute to the R^8-terms in the type IIB string effective action.Comment: 31 pages, 4 figures. v3: minor correction and reference adde

### IIA/IIB Supergravity and Ten-forms

We perform a careful investigation of which p-form fields can be introduced
consistently with the supersymmetry algebra of IIA and/or IIB ten-dimensional
supergravity. In particular the ten-forms, also known as "top-forms", require a
careful analysis since in this case, as we will show, closure of the
supersymmetry algebra at the linear level does not imply closure at the
non-linear level. Consequently, some of the (IIA and IIB) ten-form potentials
introduced in earlier work of some of us are discarded. At the same time we
show that new ten-form potentials, consistent with the full non-linear
supersymmetry algebra can be introduced. We give a superspace explanation of
our work. All of our results are precisely in line with the predictions of the
E(11) algebra.Comment: 17 page

### Non-propagating degrees of freedom in supergravity and very extended G_2

Recently a correspondence between non-propagating degrees of freedom in
maximal supergravity and the very extended algebra E_11 has been found. We
perform a similar analysis for a supergravity theory with eight supercharges
and very extended G_2. In particular, in the context of d=5 minimal
supergravity, we study whether supersymmetry can be realised on higher-rank
tensors with no propagating degrees of freedom. We find that in this case the
very extended algebra fails to capture these possibilities.Comment: 12 pages, 1 figure. v2: transformation properties of higher-rank
tensors under SU(2) R-symmetry analysed and refs added. v3: improved
discussion, published versio

### Massive Three-Dimensional Supergravity From R+R^2 Action in Six Dimensions

We obtain a three-parameter family of massive N=1 supergravities in three
dimensions from the 3-sphere reduction of an off-shell N=(1,0) six-dimensional
Poincare supergravity that includes a curvature squared invariant. The
three-dimensional theory contains an off-shell supergravity multiplet and an
on-shell scalar matter multiplet. We then generalise this in three dimensions
to an eight-parameter family of supergravities. We also find a duality
relationship between the six-dimensional theory and the N=(1,0) six-dimensional
theory obtained through a T^4 reduction of the heterotic string effective
action that includes the higher-order terms associated with the
supersymmetrisation of the anomaly-cancelling \tr(R\wedge R) term.Comment: Latex, 32 Pages, an equation is corrected, a few new equations and a
number of clarifying remarks are adde

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